# How to find out whether guassian or salt& pepper noise present in an image, Is there any algorithm

Is there any algorithm for identifying the noise in an image I have to identify whether the noise present in a mammogram image is guassian or salt& pepper.

Exploit the fact that salt&pepper noise has only 2 values and median filter does excellent job in getting rid of it.

• Filter your image with median filter
• Find pixels where median filter did most of its job
• Plot histogram of those pixels
• Compute fraction of 0s and 1s

threshold = 0.2; % adjust to perform best on your images
imd = double(im);
imd = imd./max(max(imd));
imdg = imnoise(imd,'gaussian');
imdsp = imnoise(imd,'salt & pepper');
subplot(2,2,1), imshow(imdg)
subplot(2,2,2), imshow(imdsp)
imdgf = medfilt2(imdg);
imdspf = medfilt2(imdsp);
g = imdg.-imdgf;
sp = imdsp.-imdspf;
gm = abs(g)>threshold;
spm = abs(sp)>threshold;
subplot(2,2,3), hist(imdg(gm))
subplot(2,2,4), hist(imdsp(spm))
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